1. Field of the Invention
The present invention pertains to the field of couplings suitable for the rapid fixing and releasing of optical instruments such as still and video cameras, to supporting devices such as tripods, and more particularly to the type of coupling having a releasable shoe which is attached to a camera, and a base attached to the tripod, and a means on the base allowing for the rapid mounting and release of the shoe/instrument to and from the tripod.
2. Description of the Prior Art
Optical instruments are commonly provided on their bottom surface with a standardized screw hole by which they may be mounted to a supporting device, such as a tripod. However, the operation of screwing and unscrewing the camera or other optical instrument to the supporting device is so inconvenient and time consuming as to render the use of a tripod or other supporting device impractical or cumbersome in any situation where setup speed is critical.
There are known in the prior art many designs which aim to increase the convenience and utility of camera supporting devices by providing a means for allowing the quick attachment and detachment of the camera to and from the supporting device. The various existing designs are either integral to a panhead or adapted to be mounted atop a panhead. All of the designs feature two parts: a shoe or a stud affixed to the screwhole on the bottom of the camera or other optical instrument and intended to largely remain so affixed, and a base integral to, or mountable atop a tripod panhead, which base incorporates a means for quickly fixing and releasing the shoe/stud to, and from the base.
A design frequently encountered in the prior art features a rectangular shoe, at least two opposing parallel edges of which are formed in an incline outwardly toward the bottom of the shoe, and a fixing/releasing means on the base comprising a clamp in the form of a channel with two inclined walls, one stationary and the other inwardly and outwardly movable. The shoe/camera is aligned with an open end of the channel-shaped base and then slid in to fully engage the inclined walls. The shoe/camera is then secured by manually tightening a knob provided on the base, which moves an inclined wall of the base against its opposing wall, effectively clamping the shoe. The shoe/camera is released by reversing the mounting procedure.
Although this common design is simple and easy to manufacture, it suffers some serious shortcomings in convenience and security. The fact that the shoe must first be aligned with an open end of the channel, and then pushed and guided into the base prior to mounting; and that the shoe must be clamped to the base by a screwing operation, the security of which is dependent on the degree of manual tightening, greatly reduces any advantage the device may have as a "quick"-release.
Disclosed in U.S. Pat. No. 4,929,973 to Nakatani, is a panhead with a quick-release device, the basic type and operation of which is common to many designs. This type of device features a rectangular receptacle defined in the top of the panhead which is closed on three sides and open along the forth side, and a shoe which is of a generally square or rectangular shape, and having edges inclined outwardly toward the bottom. The shoe, which is attachable to the underside of a camera, fits into the panhead receptacle. The shoe/camera can be secured therein by means of a pivotable shoe locking lever mounted on the open side of the receptacle and by means of which the shoe may be selectively secured or released, thereby allowing for the quick attachment or release of the camera to or from the panhead. However, in this prior-art quick-release and in many others of similar design, the camera/shoe can be oriented to the receptacle prior to attachment, in at most two distinct positions. The care thus required to correctly position the camera/shoe prior to attachment slows the process of affixing the camera to the supporting device. In addition, the pivoting shoe locking lever of this prior-art quick-release and many of its type must, after the placement of the shoe into the tray, be manually pushed further in the locking direction in order to ensure a secure connection. In this, and in the previously discussed prior-art quick-release, the shoe features outwardly inclined edges which are exposed and thus vulnerable to damage when not mounted in the base tray or receptacle. Also, the outwardly inclined edges of the shoes of quick-release devices of this type present a protrusion which can easily snag on clothing, straps, equipment bags, etc.
Disclosed in U.S. Pat. No. 4,795,118 to Kosugi, is a panhead which incorporates a quick-release device, the shoe of which comprises inwardly-formed working surfaces which are thus not vulnerable to damage and snagging. However, this design suffers shortcomings. After the shoe is attached to the base, a separate and distinct manual operation is required to firmly lock it. Also, this device is of such size and complexity as to be only suitable for being integral to a panhead. Furthermore, the utility and convenience of the quick-release component of this device is compromised by the fact that the shoe can be attached to, and released from the base in but a single distinct and narrowly-ranged rotational position.
The previously described prior-art quick releases have shortcomings inherent in their respective designs, as well as some shortcomings they share. The devices of Nakatani and Kosugi, as well as any of the frequently encountered quick release devices which allow the joining of the shoe to the base in few orientations only, feature shoes which are attached to the camera with a separate screw, which hinders the quick removal of the shoe from the camera should the need arise. A separate camera screw must be used, because if in the interest of ease of removal, the shoe and the camera screw were formed as a unit, the rotational orientation of the shoe with respect to the camera would, upon tightening, be entirely arbitrary. However, since the shoes of the previously described quick-releases can mate with their respective bases only in few distinct positions, an arbitrary shoe-to-camera orientation would be confusing and unacceptable, especially if one were to use two or more shoe/camera combinations on the same base/tripod--a situation common in photography. In addition, the limitation of possible mounting positions slows the shoe-to-base coupling operation by forcing the photographer to visually confirm alignment while guiding the camera/shoe to its receptacle. This is a critical drawback to a photographer intent on keeping an eye on the subject while setting up equipment.